In recent years, there have been proposed and developed various hydraulically-operated vane rotor equipped variable valve timing control (VTC) devices, capable of locking a vane rotor at an intermediate phase angular position (simply, an intermediate phase position) between a maximum phase-advance position and a maximum phase-retard position. One such hydraulically-operated vane rotor equipped variable valve timing control device has been disclosed in Japanese Unexamined Patent Application Publication No. 2012-026275 (hereinafter is referred to as “JP2012-026275”), corresponding to U.S. Pat. No. 8,677,965, issued on Mar. 25, 2014. The valve timing control device disclosed in JP2012-026275 is equipped with a driving rotary member configured to define therein a working-fluid chamber, a vane rotor fixedly connected to a camshaft and configured to partition the working-fluid chamber into a phase-advance hydraulic chamber and a phase-retard hydraulic chamber and configured to rotate in a phase-advance direction or in a phase-retard direction with respect to the driving rotary member, a phase-change mechanism configured to rotate the vane rotor with respect to the driving rotary member in the phase-advance direction or in the phase-retard direction by supplying working fluid to one of the phase-advance hydraulic chamber and the phase-retard hydraulic chamber and discharging working fluid from the other for changing a phase of the engine valve, and a position-hold mechanism configured to lock or hold a relative-rotation position of a vane rotor to the driving rotary member at an intermediate phase position between a maximum phase-advance position and a maximum phase-retard position.
The position-hold mechanism is comprised of a lock pin slidably disposed in a vane of the vane rotor, and a lock-hole structural member that is configured to be press-fitted into a recessed portion formed in a rear plate (a rear cover) of the driving rotary member for forming a lock hole with which the lock pin is brought into and out of engagement.
During an engine stopping period, the lock pin advances toward the lock hole by the spring force of a return spring. Owing to the advancing-movement of the lock pin into engagement with the lock hole, the vane rotor is locked at the intermediate phase position with respect to the driving rotary member. With the vane rotor locked at the intermediate phase position, for instance during engine cold-start operation, a good startability can be ensured.